1. Field of the Present Invention
The present invention relates to a numerical control system including a numerical controller and data communication apparatuses each having a removable filter circuit.
2. Description of the Related Art
In a numerical control system including a numerical controller and data communication apparatuses, increasing the noise immunity so that an appropriate operation is performed without causing a malfunction has been required. As a method to increase the noise immunity, there is a method of using noise suppression parts. However, taking measures against excessive noise, which is infrequently generated, for preventing malfunction leads to using a number of noise suppression parts. As a result, a data communication apparatus and a numerical control system using data communication apparatuses become expensive.
In particular, in the case of a system in which a plurality of data communication apparatuses as slave apparatuses are connected to a master apparatus, such as a numerical controller, in a daisy-chain mode, a number of data communication apparatuses are used in the entire system. Accordingly, if each data communication apparatus becomes expensive, the entire numerical control system becomes expensive.
Incidentally, various points can be considered as noise occurrence points in the numerical control system. In many cases, however, it is known that trouble in data communication between data communication apparatuses due to the influence of noise occurs when noise is superimposed on a communication cable located in a specific section within the electric panel or a power cable to supply electric power to each data communication apparatus. In addition, when noise is superimposed on the communication cable or the power cable, trouble or failure of the transmitted signal may occur.
That is, if only the noise immunity at a location where trouble has occurred in data communication due to noise can be increased, it is possible to increase the noise immunity of the entire system. In addition, it is possible to reduce the cost for noise reduction in the entire system.
If a number of noise suppression parts are used, it is possible to increase the noise immunity of the data communication apparatus so that malfunction does not occur even for excessive noise. However, the data communication apparatus and the system using the same become expensive. In particular, in a system in which a plurality of data communication apparatuses are connected to each other, a number of data communication apparatuses are used in the entire system. For this reason, there has been a problem in that the entire numerical control system becomes expensive if each data communication apparatus becomes expensive.